ford transmisson, shaft length, drive shaft

will a c3 and a c4 interchange in a 1980 fairmont inline 6 cylinder

Answer
    They both use the same bolt pattern to the block.  You'll have to get a different torque converter and I'm not sure if the drive shaft length would be the same.  May be some problems with the linkage, but that would be easy to change.  Speedo cable length might also be off.  But, they couldn't be too different, people swap them all the time.
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